X-rays involving 15,000 patients stolen in Mich.

That’s according to a letter the Detroit-based hospital system sent to patients.

The Detroit Free Press reports Monday thieves may have taken the X-rays involving 15,417 patients because of the silver that’s contained in them.

Henry Ford spokesman David Olejarz says the silver interacts with radiation to allow for a clearer image.

The stolen X-rays were dated between 1996 and 2003. The letter sent to patients says names, addresses and dates of birth may have been included on the X-rays, but health insurance numbers and social security numbers were not.